1. Field of the Invention
This invention relates to a novel synthetic crystalline zeolite and to methods for its preparation. More particularly, this invention relates to a novel synthetic crystalline aluminosilicate having catalytic properties, to methods for preparing the same, and to hydrocarbon conversion therewith.
2. Description of the Prior Art
Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic capabilities for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure within which there are a large number of small cavities which are interconnected by a number of still smaller cavities. These cavities and channels are uniform in size. Since the dimensions of these pores are such as to accept for absorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as "molecular sieves" and are utilized in a variety of ways to take advantage of these properties.
Such molecular sieves include a wide variety of positive ion-containing crystalline aluminosilicates, both natural and synthetic. These aluminosilicates can be described as a rigid three-dimensional network of SiO.sub.4 and AlO.sub.4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen is 1:2. The electrovalence of the tetrahedra-containing aluminum is balanced by the inclusion in the crystal of a cation, for example, an alkali metal or an alkaline earth metal cation. This can be expressed by a formula wherein the ratio of Al to the number of the various cations, such as Ca/2, Sr/2, Na, K or Li, is equal to unity. One type of cation has been exchanged either in entirety or partially by another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange it has been possible to vary the size of the pores in the given aluminosilicate by a suitable selection of the particular cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic crystalline aluminosilicates. These aluminosilicates have come to be designated by letter or other convenient symbol, as illustrated by zeolite A (U.S. Pat. No. 2,882,243), zeolite X (U.S. Pat. No. 2,882,244), zeolite Y (U.S. Pat. No. 3,130,007), zeolite K-G (U.S. Pat. No. 3,055,654), zeolite ZK-5 (U.S. Pat. No. 3,247,195), zeolite .beta. (U.S. Pat. No. 3,308,069), zeolite ZK-4 (U.S. Pat. No. 3,314,752), zeolite ZSM-5 (U.S. Pat. No. 3,702,886), zeolite ZSM-11 (U.S. Pat. No. 3,709,979), zeolite ZSM-12 (U.S. Pat. No. 3,832,449), and zeolite ZSM-35 (U.S. Pat. No. 4,016,245).